Demand valve assembly

ABSTRACT

Demand valve assembly and method for delivery of gases to a patient having a valve body with an outlet adapted to be connected to a patient adapter and an inlet in communication with the outlet for receiving the gases from a high pressure source. Valve means is disposed in the inlet. A distensible generally ellipsoidal bag is connected to the valve body for controlling the operation of the inlet valve as the bag changes its dimensions along its major axis in response to patient breathing. An additional chamber is in communication with the inlet for creating an intermediate pressure which can be used for humidification of the gases or entraining medicants therein. Valve means are provided between the intermediate pressure in the additional chamber and the low pressure contained in the valve body and the distensible bag. In the method, the changes in the dimension in the bag along its major axis are sensed to control the feeling of the bag.

United States Patent 1 Weninger July 16, 1974 [54] DEMAND VALVE ASSEMBLY j o i Cline sslstant xammer-- ra azarus [75] Invent ii Cathedral or e m or tFim-lr ghrsytna ntsre a1 Albritton & Herbert W w [73] Assignee: Bird Corporation, Palm Springs,

Cahf' 57 1' ABSTRACT [22.] Flled: June 1972 Demand valve assembly and method for delivery of [21] Appl. No.:- 264,395 gases to a patient having a valve body with an outlet adapted to be connected to a patient adapter and an [52] U S Cl 137/613 251/61 2 137/1316 9 inlet in communication with the outlet for receiving [51] A6lm 16/00 i 3 the gases from a high pressure source, Valve means is [5'8] Fie'ld 251/20 53 61 61 l disposed in the inlet. Adistensible generally ellipsoidal 251/61 2 4 61 137/163 bag is connected to the valve body for controlling the R l28/1'42 2 14 i 146 4 4 5 operation of the inlet valve as the bag changes its diy mensions along its major axis in response to patient breathing. An additional chamber is in communication [56] References c with the inlet for creating an intermediate pressure UNITED STATES PATENTS which can be used for humidification of the gases or ,473 5/1938 Smith etal /6 XY entraining medicants therein. -'Valve means are prog gggffig wi vided between the intermediate pressure in the addi- O nson eta 3,386,458 6/1968 Wasserman 137/613 x ss gz gggygj ifig gi g g g if comamed m 3,547,143 12/1970 Mills,-.Ir. 137/613.X 3,587,642 6/1971 Gotzenberger 137/613 X In the method, the changes in the dimensions in the 3,604,445 9/197,l Jordan 137/613,X bag along its ,major axis are sensedto control the 3,747,600 7/1973 rhndersson ....128/188 "fi n so the bae-.. s, I

see-w se 5 Claims, 3 Drawing Figures '1 a DEMAND VALVE ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention v The invention relates to a demand supply valve for delivery ofa gas to a patient such as humidified analgecreased patient effort at a time when the patient is experiencing decreased respiratory response in the event analgesia gas is being administered. This may cause hypoventilation which is obviously undesirable in such a criticalphase. Also, in prior art devices, the desired control of humidity and entrainment of medication in the gases to provide optimum comfort within the patients breathing passages has been a problem. Continuous nebulization and humidification maybe undesirable, since the injection of medicants and moisture into the gas stream is not a function of the patient demand.

Different patients or different phases of treatment of the same patient will create different demand rates for the equipment. Administration of analgesia gases to patients experiencing intermittent high pain levels, requires intermittent flow rates generally higher than those available from usual gas supply systems. It can be seen from these considerations that a genuine need exists for a new and improved demand valve which can provide high flow rates for limited time intervals with minimum patient breathing effort, and which maintains desirable comfort levels in the'patients breathing passages.

SUMMARY OF THE. INVENTION A demand valve assembly which is utilized for administering a gas from a source to a patient undera positive pressure and is comprised of a valve body having a flow passage therein. The body is formed with an outlet in communication with the flow passage and which is adapted to be connected. to the patient. A one-way check valve or umbrella valve actuated by low differential pressure, in the range of one-half centimeter of water, is mounted within the outlet to allow flow of gas to the patient initiated by patient breathing.

The valve body is also provided with an inlet in communication with the flow passage and carries a valve seat which surrounds the inlet and a valve member movable between open and closed positions with respect to the valve seat. The valve body is provided with an additional opening in communication with said flow passage. A generally ellipsoidal distensible bag is connected to the body at the additional opening and is in communication with the flow passage. Inlet valve operating means is mounted in the bag for sensing the length of the major axis of the bag for controlling the movement of said valve member between the open and closed position thereby controlling the filling of said bag. An additional pressure chamber is provided within the chamber formed by the bag and the valve body and is in communication with the flow passage through a poppet valve mounted in the additional chamber. An outlet in the valve body in communication with the additional chamber isprovided and contains a valve means which is yieldably urged away from its seat by attaching equipment which provides for humidification of the gases and entrainment of medicants therein.

In the method for delivery of a gas to a patient from a source under high pressure by the use of an ellipsoidal distensible bag,,the length of the major axis of the bag is sensed to control the filling of the bag with gases at a low pressure. A smaller volume of gas at an intermediate pressure is created for use in humidifying and entraining medicants in the gas stream. Delivery of the gas in the bag is made on demand by the patient.

In general it is an object of the present invention to provide a demand valve assembly and method which supplies analgesia or anesthesia gas to a patient upon creation of very low differential pressure by the patients breathing.

Another object of the present invention is to provide a demand valve assembly and method of the above character which supplies analgesia or anesthesia gas to the patient only on patients demand.

Another object of'the present invention is to provide a demand valve assembly and method of the above character which suppies analgesia or anesthesia gas to a patient with the least effort on the patients part when inhaled so as to avoid hypoventilation.

Another object of the present invention is to provide a demand valve assembly and method of the above character which supplies humidification and nebulization on a demand basis to thereby provide closer control of gashumidity and volume of medicants injected into the gas stream. Another object of the present invention is to provide a demand valve assembly and method of the above character which supplies high instantaneous analgesia gas flow rates on demand by the patient for limited periods of time.

Another object of the present invention is to provide a demand valve assembly and method of the above character which provides automatic availability of an emergency source of the gas in use in the unlikely event that the simplified valving mechanism should fail, or in the event that the gas supply connected to the valve body inlet should become depleted. H

These and other objects of the present invention will become apparent from the drawings and from the description of the preferred embodiments as set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view passing through the center line of a demand valve assembly incorporating the present invention.

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is a blockdiagram of a system incorporating a demand valve assembly showing the physical connection between the major components of the system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The. demand valve assembly 11 incorporating the present invention in which the present method is performed consists of a valve body 12 formed of a suitable material such as aluminum. It is provided with a flow passage 13 extending therethrough. An outlet fitting 14 is threaded into the body 12 forming a seal between a shoulder 15 on the fitting 14 and the outside surface of the body 12 as shown in FIG. 1. The fitting 14 is provided with an outlet opening 16 in communication with the flow passage 13 and is adapted to be placed in communication with the patient as hereinafter described.

A check valve assembly 17 is provided within the valve body 12 and serves to permit only one-way flow through the passage 13, from the flow passage 13 through the outlet opening 16. The valve assembly 17 consists of a circular valve seat member 18 which is provided with a cylindrical depending skirt-like portion 19 which is fitted within the flow passage 13. The outlet valve seat member 18 is provided with a plurality of small holes'20 which are formed on a hole diameter and which are adapted to be covered by a valve mem ber 22 which is generally dish shaped or umbrella shaped, as shown in FIG. 1, with its outer annular margin 23, in engagement with the outer annular margin 24 of the valve seat member 18. The valve member 22 is formed of a suitable flexible material such as an elastomer, and is provided with a tit 25 which extends through a hole 26 in the valve seat member 18 for retaining the same.

An inlet valve assembly 30 is mounted in a bore 31 in the body 12 extending into the flow passage 13. The inlet valve assembly 30 consists of a fitting 32 which is mounted within the bore 31. The fitting 32 is provided with a flange 33 which seats within an annular recess 34 provided on the inside of the body 12.

The outer extremity of the fitting 32 is provided with threads 35 to permit the same to be secured to a source of gas as hereinafter described. An 0 ring 36 is seated in an annular recess 37 adjacent to the threads 35 and serves to seal the junction between the inlet valve as sembly fitting 32 and the valve body 12 as well as the fitting which is connected to the source of gas. The fitting 32 is provided with a large bore 40 extending axially of the same and which is in communication with a small axial bore 41 which is surrounded at the junction ofthe two bores by a valve seat 42. An inlet valve member 43 having a cone-like tip portion 44, of a suitable non-abrasive material such as viton, and having a brass anterior body with an internally threaded blind bore 46 is adapted to be moved between open and closed positions with respect to the valve seat 42.

The inlet valve assembly fitting 32 is ofa suitable material for a pneumatic fitting such as brass, and is secured in place in the inlet valve assembly bore 31 by a combination of friction forces and the flange 33 on the fitting 32 in contact with the body recess 34. The outside diameter of the fitting 32 has an annular groove 47 between the flange 33 and the external threads 35 and a radial hole 48 extending between the large bore 40 and the bottom of the groove 47.

A bag adapter fitting 51 is threaded into the body 12 forming a seal between a shoulder 52 on the fitting 51 and the outside surface of the body 12 and is provided with a flow passage 53 which is in communication with the flow passage 13. Means is provided for forming a first chamber 54 for receiving gases with which the valve assembly 11 is to be utilized, and consists of a distensible generally ellipsoidal bag 55 formed of a suitable elastomer such as rubber. The bag is provided with an opening 56 at one end of the major axis which is re inforced as shown and which is adapted to fit snugly 4 over the outside diameter of the bag adapter fitting 51 as shown in FIGS. 1 and 2. A small flange 57 is formed on the outside diameter of the bag adapter 51 where the bag 55 is mounted to assist in providing a seal between the bag adapter 51 and the bag 55.

The bag as shown has major and minor axes which are at right angles to each other. Means is provided for sensing-the length of one of the axes, for example, the major axis as shown, for controlling the movement of the inlet valve member 43 between the open and closed positions. Such inlet valve operating means 60 extends between the inlet valve member 43 along the major axis to the inside wall of the distensible bag 55. An inlet valve operating means adjustable member 61 is formed of a suitable non-abrasive material such as delrin. The adjustable member 61 has a blind threaded bore 62 concentric with its cylindrical axis. The opposite end of the adjustable member 61 has a smooth spherical radius 62. A rod 64 is formed with a larger diameter 65 on one end and a smaller diameter 66 on the opposite end. Both the diameters 65, 66 have external threads at the end. The threads on the larger diameter 66 are formed to mate with the threads in the bore 62 of the adjustable member 61'. A valve stem 67 inthe shape of a rod has a blind threaded bore 68 on one end and a smaller diameter 69 having external threads on the other. The threads in the bore 68 are formed to mate with the external threads carried on the small diameter 66 on the rod 64. The threads on the small diameter 69 are formed to mate with the threads in the bore 46 in the anterior body of the inlet valve member 43.

Means is provided for forming a second chamber in which a second volume of gas is collected at a pressure which is higher than that within the gas collected in the bag 55 and in this embodiment consists of an inlet shroud 71 which forms a second chamber 72. The-inlet shroud 71 is formed of a suitable material such as brass tubing and is hermetically sealed to the inlet valve assembly fitting 32 as shown in FIGS. 1 and 2. The tubing forming the inlet shroud 71 has flats 73 formed midway along its length, and external threads 74 on the end opposite theone to which is mounted inlet valve fitting 32.

The inlet valve operating means 60 extends through the center of the inlet shroud 71.. A pressure reduction valve seat 75 is formed on the inside diameter surrounding the open end of the inlet shroud 71. A pressure reduction valve member 76 is mounted on the small diameter 66 of the rod v64. The pressure reduction valve 76 is formed of a suitable soft non-abrasive material such as delrin, and has an axial bore 77. The bore 77 has a small diameter 78 at one end formed to fit the small diameter 66 of the rod 64. An annular recess 79 is formed on the end of thereduction valve member 76 having the small diameter bore 78. A larger diameter bore 81 at the other end of the reduction member 76 forms a skirt 82 allowing gases to pass between the smaller diameter 66 of the rod 64 and the skirt 82. The skirt 82 has radial holes 83 allowing gas flow between the second chamber 72 and the face of the reduction valve member 76. An external annular groove 84 is formed on the skirt 82. An 0 ring 85 is disposed within the groove 84 and serves as a guide for the reduction valve member 76 as it contacts the inside diameter of the inlet shroud 71 forming the second chamber 72.

A spring retainer 86 of a suitable material such as brass, having a generally cylindrical shape with externally available wrench flats 87, hasa deep bore on the axis of the cylinder forming a well 88, and a smaller diameter bore 89, also on the axis of the cylinder, through the bottom wall of the well 88. The wall of the spring retainer 86 forming the well 88 has a plurality of radial holes 92 near the bottom of the well 88. The spring retainer 86 also has internal threads 93 in the well 88 which are formed to mate with the external threads 74 on the end of the inlet shroud 71.

A compression spring 94 is disposed in the well 88 and extends between the bottom of the well 88 and the annular recess 79 provided on the end of the reduction valve member 76. A locknut 95 is threaded on the inlet shroud threads 74 prior to placement of the spring retainer 86. The locknut 95 is used to secure the spring retainer 86 following adjustment as hereinafter described.

A safety valve means 98 is mounted in an opening 99 in the valve body 12 and is in communication wih the flow'pa'ssage 13. The opening 99 is shaped to receive a safety valve member 100 formed of some suitable elastomer, which is retained in the opening99 by a safety valve seat member 101 having a hole 102 through its center. The safety valve seat member 101 is shaped so that it may be pressed into the safety valve opening 99 and retained in place by friction between the valve body 12 and the seat member 101 and has a safety valve seat 103 surrounding the hole 102. The

shape of the safety valve seat member 101 is such as to generate internal stresses within the safety valve member 100 which yieldably urge the saftey valve member [00 toward the closed position against the safety valve seat 103.

The valve body 12- has an auxiliary opening 106 which is in communication with the inlet valve assem bly bore 31. The auxiliary opening 106 is also in communication with the second chamber 72 through the radial hole 48 extending through the bottom of the annular groove 47 on the inlet valve assembly 32.

An auxiliary fitting 107 is provided having a tapered axial hole 108, and is threaded into, the auxiliary opening 106. The fitting 107 has an auxiliary valve seat 109 surrounding the tapered hole 108 on the threaded end. An auxiliary valve member, such as the poppet valve 110, is disposed in the opening 106 and is yieldably urged against the auxiliary valve seat 109 by .a compression spring 111 carried in the well formed by the auxiliary opening 106. The auxiliary valve member 110 is formed of a suitable soft non-abrasive material such as delrin and has an annular groove 112 in which is disposed an O ring 113 of a suitable elastomeric material which makes contact with the auxiliary valve seat 109 when the auxiliary valve member 110 is in the closed position. A stem 114 extends below the head of the auxiliary valve member 110 toward the external opening in the fitting 106. The stem 114 iscontacted by a mating fitting when it is inserted into the tapered hole 108 to yieldably urge the valve member 110 and the O ring 113 awayfrom the auxiliary valve seat 109 toward the open position.

F IG. 3 best illustrates the role played by the demand valve assembly 11 in a system for administration of analgesia or anesthesia gases to a patient. A gas supply 117 is delivered to a mixing valve 118. The mixing valve 118 may be of a type such as that shown in U.S.

Pat. No. 3,331,368. The mixed gas, still at the pressure of the supply 117, is directed through piping to the demand valve assembly 11. The reduction in supply pressure achieved in the'second chamber 72 is made available through the auxiliary fitting 107 to a nebulizer l 19 of a standard type such as that shown in U.S. Pat. No. 3,172,406. For the purposes of this embodiment the pressure in the second chamber 72 is in the range of 10 to 12 psi. The gas pressure is further reduced from the second chamber 72 to the first chamber 54 through the reduction valve 75. Gas at the low pressure contained in the first chamber 54 is made available to a patient when a differential pressure across the outlet valve 22 in the range of one-half centimeter of water is created by the patients inhalation. The output from the nebulizer 119 is joined with the inhalation gases downstream of the demand valve assembly 11 and upstream of a patient adapter 120. The patient adapter 120 is of a standard type such as that found' in U.S. Pat. No. 3,467,092.

The demand valve assembly provides a method of delivering properly mixed gases to a patient from a pressurized supply'by creating a low pressure variable volume reservoir of gas through sensing dimensional changes in the reservoir, and holding the gas in the reservoir for delivery on demand to the patient. The method also includes utilizing an intermediate pressure in a small volume of gas and making the small volume available to a nebulizer. The output of the nebulizer is directed back into the flow of gas to the patient. The method further includes providing an emergency gas supply to become availableto the patient in the event of mechanical malfunction or depletion of the original gas supply. 1

Operation and use of the demand valve assembly under various sets of circumstances may now be briefly described as follows. Let it be assumed that gas supply 117 at a pressure at least as high as that required in the second chamber 72, 10 to 12 psi for this embodiment, is available to the mixing valve 119. Also let it be assumed that-all valves are set to provide acontinuous supply of the desired type of gas of the desired mixture at the demand valve inlet opening 41. Adjustments are made to the inlet valve operating means adjustable member 61 which controls the pressure contained in the firstchamber 54. For example, as the adjustable member 61 is rotated on its threads so as to lengthen the inlet valve operating means 60 a smaller decrease in themajor diameter of the distensible bag 55 will urge the valve member 44 onto its seat 42 at the inlet opening 41. It can be seen that the shape of the bag 55 is a function of the difference between the pressure in the first chamber 54 and the ambient pressure. The major diameter of the bag 55 decreases as the pressure differential increases. Thus an increase in the length in the inlet valve operating means 60 by adjustment of the member 61 will allow a smaller differential pressure between the gases contained in the first chamber 54 and the ambient pressure before the inlet valve member 43 shuts off the supply 117. For the purposes of this description the pressure in the first chamber 54 is set at approximately one-fourth centimeter of water before the supply 117 is shut off. I The pressure reduction valve member 76 is adjusted to maintain a difference between the pressure in the second chamber 72 and the pressure in the first chamber 54 equivalent to 10 psi above ambient pressure. To

' 7 obtain this adjustment the spring retainer 86 is turned clockwise or counter-clockwise on its threads by engaging external flats 87 with a suitable tool thus varying the compressed length of the Compression spring 94 by varying the depth of the well 88 in the spring retainer 86. The reduction valve member 76 closing force comprised of the adjusted force stored in the compression spring 94 together with the piston force provided by the pressure in the first chamber 54 against the end of the valve member 76 exposed to the first chamber 54 is now equivalent to the force urging the valve member 76 open due to 10 psi on the surface of the valve member 76 exposed to the second chamber 72. Following the foregoing adjustment, locknut 95 is jammed against the end of the spring retainer 86 by rotating it on its threads while retaining the spring retainer 86 from rotation by engaging its flats 87, thus locking the adjustment into the reduction valve member 76.

Let it be assumed that the demand valve assembly 11 is to be used with a patient who is experiencing high intermittent pain levels, as for example,'in the field of obstetrics when a woman is experiencing labor pains. High flow rates for limited periods of time in the range of 250 liters per minute are often demanded. Conventional systems for supplying analgesia gases are incapable of supplying flow rates of this magnitude. The demand valve assembly 11 described herein carries a substantial reservoir for the storage of gas in the distensible bag 55 from which these high flow rates may be obtained. i

The outlet valve member 22 functions as a one-way check valve means since high pressure on the downstream side will tend to close the valve 22 more securely. The force urging the valve 22 closed will resist flow in the normal direction until a differential pressure across the valve member 2 2 of approximately one-half centimeter of water is created. Then the valve member 22 will open and permit outward flow to the patient only. Since the pressure in the first chamber 54 is maintained at one-fourthcentimeter of water, the patient need only create a vacuum on the downstream side of the outlet valve member 22 of one-fourth centimeter of water. Upon inhaling to the extent of creating such a vacuum valve member 22 opens and the entire reservoir of gas contained in the first chamber 54 is directly available to the patient. Depletion of the gas from the reservoir drops the pressure in the chamber 54 to some value less than one-fourth centimeter of water. The major diameter of the bag 55 increases as the minor diameter decreases due to the drop in pressure, and the inlet valve member 43 is vurged away from the inlet valve seat 42 by a combination of the piston force on the inlet valve member 43 at the inlet opening 41 and the force of gravity on the inlet valve operating means 60. Gas begins to flow into the second chamber 72 through the inlet 4]. The yicldable force combination from the compression spring 94 and the pressure in the first chamber 54 is now insufficient to maintain the reduction valve member 76 in the closed position against the reduction valve seat 75. Gas then begins to flow from the intermediate pressure volume in the second chamber 72 to the lower pressure volume in the first chamber 54.

The volume of gas in the second chamber 72 is relatively small and the flow toward the first chamber 54 through the reduction valve 75 would be insubstantial if the supply 117 were not made immediately available 8 V to the chamber 72 through the inlet 41. Additionally, in the case Where the nebulizer 119 is attached to the fitting 107, the pressure in the second chamber 72 bleeds off toward ambient pressure in the second chamber during the latter stages of the expiratory phase when the reduction valve member 76 is in the closed position. It can be seen that the large volume of gas which must be made available to the patient immediately from the first chamber 54 is being replaced in part during the patients inspiratory phase and the replenishment is substantially completed during the earlier stages of the patients expiratory phase.

It is usual that while a patient is receiving analgesia gas he is also experiencing decreased respiratory response. As heretofore mentioned, the patient need create only a low negative pressure, in the range of onefourth centimeter of water,to open the outlet valve assembly 17 and receive the gas from the reservoir 54. This minimal breathing effort required on the part of the patient is of special advantage in avoiding hypoventilation, or under breathing, which may result because of the aforementioned decreased respiratory response. The possibility of hypoventilation is enhanced if the patient is required to exert greater effort in breathing, as is the case when utilizing most other equipment serving this function.

The distensible bag 55 serves not only as a reservoir, but as a highly sensitive diaphragm which converts small differential pressures across the diaphragm into relatively large translational motion. The distensible bag 55 in its ellipsoid shape suffers less mechanical deterioration from the cyclic differential pressures due to the omnidirectional characteristics of internal stress within the material of the bag 55, and a relatively small magnitude of material stress due to the small differential pressures. Neoprene and natural rubber deteriorate morerapidly in areas of higher tension or unequal distribution of stress. Portions of unequal distribution of stress in the bag material are relatively small, being only in the vicinity of the bag adapter fitting 51 and the point where the inlet valve operating means adjustable member 61 contactsthe inside wall of the bag 55.

The center point of the diaphragm like member provided by the bag 55 which is contacted by the inlet valve operating means adjustabl'emember 61 can be seen to translate directionally out of phase with the'direction of translation provided by the center point of a normal diaphragm. In the case of'a normal diaphragm the center point will translate away from the volume of greater pressure. Due to the initial ellipsoid shape of the bag 55 and its tendensy to approach a spherical shapeas the pressure contained therein rises, the tendency is for the major diameter to shorten as the minor diameter increases due to a rise in pressure, and the center point of the bag is caused to translate directionally toward the volume of higher pressure. The ellipsoid shape of the bag 55 also provides a greater inside area than that which would be available from a tautly stretched diaphragm, which in turn provides larger translational movement at the center of the diaphragm provided by the distensible bag 55 than would be experienced at the center of the taut diaphragm for the same differentials in pressure.

Let it be assumed that there exists a requirement for a patient to be delivered medication suspended within the stream of gas. Let it also be assumed that it is desired to humidify the gas stream to prevent dryness .from being created within the patients breathing passages by the passage of the gas stream. In such an instance the nebulizer 119 is connected at the fitting 107 which urges the auxiliary valve member 110 to the open position, This occurs as the O ring 113 disposed in the annular groove 112 on the auxiliary valve member 10 is urged away from the auxiliary valve seat 106 by contact between the connecting member attached to the nebulizer 119 and the stem 114 of the, auxiliary valve member 110, overcoming the yieldable closing up to one-fourth centimeter of water, and the inlet valve assembly 30 closes the inlet opening 41. It can be seen that the second chamber 72 is still in direct communication with nebulizer 119 through the fitting 107. It should be noted that the volume in the second chamber 72 is comparatively small. The pressure bleeds off through the fitting 107 to the nebulizer 109 almost instantaneously. Thus nebulization stops. Nebulization recurs only upon subsequent inhalation by the patient which reopens the inlet valve assembly as hereinbefore described, supplying the nebulization demand characteristic.

In the event the demand valve assembly 11 experiences mechanical failure, safety valve means 98 in the form of an elastomeric safety valve member 100 is provided to continue the delivery of the gas to the patient as before. For example, if the inlet valve operating means 60 should stick in the closed position, the gas supply 117 would no longer be available to the patient. Inhalation by the patient to the point where a negative one-fourth centimeter of water pressure is created in the outlet fitting 14 would urge the outlet valve member 22 toward the open position. Gas from the first chamber 54 would begin to be delivered to the patient. Continuing inhalation by the patient would exhaust the supply stored in the reservoir 54 and decrease the pressure therein to a point where inhalation by the patient created a negative pressure in the first chamber 54 of approximately one centimeter of water. The safety valve member 100 would be urged away from the safety valve seat 103 against yielding internal stress forces intentionally set up within the valve member 100 by the safety valve seat member 101 at assembly. A continuing supplyof gas at ambient pressure is thus made available to the patient from the emergency gas reservoir 121. The safety valve means 98 would function in the same manner to provide the emergency gasv supply 121 to the patient should the gas supply 117 become depleted.

From the above description it is evident that the invention claimed herein operates at extremely small differential pressures, in the range of 0.0003 atmospheres. The gas is delivered only on demand by the patient without undue breathing effort on his part. Patient comfort and controlled medication are provided through the demand nebulization feature. High flow delivery rates are available fromthe large reservoir provided in the distensible bag rendering the demand 10' valve particularly useful with patients requiring intermittent high flow rates because experiencing intermittent high levels of pain. In the event of mechanical valve failure or depletion of the gas supply the patient is afforded'prote'ction in the immediate and automatic availability of an emergency gas supply.

I claim:

1..An apparatus for supplying a gas to a patient from a source under a positive pressure, a valve body, said valve body having a flow passage therein, said valve body having an outlet in communication with said flow passage and adapted to be connected to the patient, said valve body having an inlet in communication with said flow passage, first valve means including a valve seat surrounding said inlet and a valve member movable between open and closed positions with respect to said valve seat, said body including a first opening in communication with said flow passage, a distensible generally ellipsoidal bag connected to said body at the first opening and forming a chamber in communication with said flow passage in said body, said bag having minor and major axes, means for sensing the length of the major axis of said bag including a valve operating member connected between said bag and said valve member to move the latter between said open and closed positions responsive, respectively, to lengthening of said major axis as said bag collapses and shortening of said major axis as said bag expands for controlling the 'filling of said bag, said valve operating member including a rigid member extending between the inside of the ellipsoidal bag-and the valve member, and means to selectively extend and retract the length of said rigid member to vary the limit of gas pressure within said bag which is effective to cause said valve member to move to its closed position.

2. An apparatus as in claim 1 wherein said bag forms a first chamber together with means forming a second chamber within said first chamber which is in communication with said inlet, and second valve means carried by the means forming the second chamber for establishing communication between the first and second chambers.

3. An apparatus as in claim 2 wherein said inlet valve operating means extends through the means forming a second chamber and said second valve means, and wherein said second valve means includes a second valve seat surrounding the inlet valve operating means and having a second opening establishing a communication between said first and second chambers and a second valve member mounted for movement between open and closed positions with respect to the second valve seat, and means yieldably urging said second valve member toward a closed position.

4. An apparatus as in claim 2 wherein said body has an auxiliary outlet-in communication with the second chamber, auxiliary valve means carried by the body for controlling the flow of gas through the auxiliary outlet, said valve means including an auxiliary valve seat surrounding said outlet, an auxiliary valve member mounted for movement between open and closed positions with respect to the valve seat, and means yieldably urging said vavle member against said seat.

5. An apparatus as in claim 4 together with a nebulizer mounted on said body, having an inlet in communication with said auxiliary outlet, whereby said auxiliary valve member is moved to the open position. 

1. An apparatus for supplying a gas to a patient from a source under a positive pressure, a valve body, said valve body having a flow passage therein, said valve body having an outlet in communication with said flow passage and adapted to be connected to the patient, said valve body having an inlet in communication with said flow passage, first valve means including a valve seat surrounding said inlet and a valve member movable between open and closed positions with respect to said valve seat, said body including a first opening in communication with said flow passage, a distensible generally ellipsoidal bag connected to said body at the first opening and forming a chamber in communication with said flow passage in said body, said bag having minor and major axes, means for sensing the length of the major axis of said bag including a valve operating member connected between said bag and said valve member to move the latter between said open and closed positions responsive, respectively, to lengthening of said major axis as said bag collapses and shortening of said major axis as said bag expands for controlling the filling of said bag, said valve operating member including a rigid member extending between the inside of the ellipsoidal bag and the valve member, and means to selectively extend and retract the length of said rigid member to vary the limit of gas pressure within said bag which is effective to cause said valve member to move to its closed position.
 2. An apparatus as in claim 1 wherein said bag forms a first chamber together with means forming a second chamber within said first chamber which is in communication with said inlet, and second valve means carried by the means forming the second chamber for establishing communication between the first and second chambers.
 3. An apparatus as in claim 2 wherein said inlet valve operating means extends through the means forming a second chamber and said second valve means, and wherein said second valve means includes a second valve seat surrounding the inlet valve operating means and having a second opening establishing a communication between said first and second chambers and a second valve member mounted for movement between open and closed positions with respect to the second valve seat, and means yieldably urging said second valve member toward a closed position.
 4. An apparatus as in claim 2 wherein said body has an auxiliary outlet in communication with the second chamber, auxiliary valve means carried by the body for controlling the flow of gas through the auxiliary outlet, said valve means including an auxiliary valve seat surrounding said outlet, an auxiliary valve member mounted for movement between open and closed positions with respect to the valve seat, and means yieldably urging said vavle member against said seat.
 5. An apparatus as in claim 4 together with a nebulizer mounted on said body, having an Inlet in communication with said auxiliary outlet, whereby said auxiliary valve member is moved to the open position. 